In the design of electronic systems using integrated circuitry it is convenient to provide standardized printed-circuit boards with a conductor array capable of supplying a variety of modular units having different sets of terminal pins. The connections between these pins and the supply conductors should be as short as possible and the conductors themselves ought to be so distributed on the board that switching operations carried out on any associated modular unit will not objectionably affect the voltages fed to the remaining loads.
An elegant solution of this problem involves the complete metallization of one face of such a board, the metallic layer on that face then acting as a common ground conductor for all the modular units connected to the ungrounded supply terminal by a set of conductor strips disposed on the opposite face. The resulting close spacing between these live strips and the grounded layer, corresponding to the thickness of the dielectric substrate of the board, minimizes the voltage drop along the strips induced by switching signals in the integrated circuits connected thereto. This solution, however, frequently requires an insulation of the grounded layer from other circuit elements by the provision of two dielectric plates between which that layer is sandwiched; the exposed faces of both plates can then be used to accommodate integrated chips or other loads to be connected across the d-c source. A drawback of such a stacked printed-circuit board, however, resides in the inaccessibility of the grounded layer so that even minor defects thereof make it necessary to discard the board.